Adult Swim has more or less always had a reputation for most of their original programming being cheap to produce, and "stylistic suck" is a common trope among certain shows. In fact IIRC one of the reasons why Korgoth never premiered despite being picked up initially was because it was discovered shortly afterwards the budget required to keep the animation quality as high as the pilot was simply too high for a full season.

This is why even some of Adult Swim's more detailed shows still have limited animation (like Metalocylpse had a lot more detail to the characters and backgrounds compared to most AS shows, but the animation was still very limited and done in flash to save money).